An organic electroluminescence device (hereinafter, referred to as an organic EL device) includes a pair of electrodes formed on a substrate and an organic compound layer including an emitting layer provided between the pair of electrodes.
At least one of the pair of electrodes of the organic EL device is provided by a transparent electrode, which is formed on a transparent substrate. As a material for forming the transparent electrode, a light transmissive material such as ITO and IZO (trademark) is used. For instance, in an organic EL device, light from the organic compound layer is transmitted through the transparent electrode and the transparent substrate to be extracted outside.
The material for forming the transparent electrode has a larger electrical resistance than metals. Accordingly, when the transparent electrode is planarly formed in a large area on the substrate, voltage declines sharply. Consequently, in the organic EL device, a luminance intensity in a surface of the substrate becomes uneven. This unevenness of the luminance intensity becomes prominent as separating from a component (e.g., an electrode pad) for supplying electricity from an exterior power supply to the transparent electrode since the luminance intensity is more largely influenced by the voltage decline.
In view of this, a method of providing an auxiliary electrode has been disclosed in order to decrease the voltage decline caused by the transparent electrode (see, for instance, Patent Literatures 1 to 3).
Patent Literature 1 discloses an electroluminescent panel to be also used as a light source of an illumination unit. The electroluminescent panel includes a substrate, a first electrode on the substrate, an auxiliary electrode formed on the first electrode, an emitting layer that is formed on the first electrode and the auxiliary electrode and defines an emitting region, and a second electrode formed on the emitting layer.
In the electroluminescent panel disclosed in Patent Literature 1, the auxiliary electrode and the emitting layer are in direct contact with each other. Accordingly, a luminescence intensity from the emitting layer around the auxiliary electrode becomes large, resulting in unevenness of the luminance intensity.
A method of avoiding unevenness of the luminance intensity occurring even when such an auxiliary electrode is provided is disclosed in, for instance, Patent Literatures 2 and 3.
Patent Literature 2 discloses a luminescence unit including a transparent substrate, a transparent electrode formed on the transparent substrate, a luminescence function layer formed on the transparent electrode, a metal-made backside electrode formed on the luminescence function layer, a first auxiliary electrode provided on the transparent electrode, and a second auxiliary electrode provided on the backside electrode. By positioning the first and second auxiliary electrodes so as not to face each other across the luminescence function layer, unevenness of the luminance intensity is inhibited.
Patent Literature 3 discloses an organic EL emitting unit to be also used as an illumination unit. In the organic EL emitting unit, a transparent electrode is formed on a transparent glass substrate, an auxiliary substrate in a predetermined pattern is formed on the transparent electrode, and the auxiliary electrode is coated with an insulative layer of a laminate structure. Moreover, an organic EL layer is formed on the transparent electrode. An opposing electrode is provided to cover the insulative layer and the organic EL layer. In the organic EL emitting unit, since the auxiliary electrode is coated with the insulative layer so that the auxiliary electrode and the organic EL device are not in direct contact with each other, unevenness of the luminance intensity is inhibited.